首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   304874篇
  免费   1786篇
  国内免费   649篇
化学   146405篇
晶体学   4476篇
力学   15084篇
综合类   6篇
数学   46526篇
物理学   94812篇
  2020年   1970篇
  2019年   2265篇
  2018年   10952篇
  2017年   11675篇
  2016年   8000篇
  2015年   3118篇
  2014年   3933篇
  2013年   9384篇
  2012年   10885篇
  2011年   19882篇
  2010年   12525篇
  2009年   12564篇
  2008年   17841篇
  2007年   21236篇
  2006年   7834篇
  2005年   12993篇
  2004年   9276篇
  2003年   8898篇
  2002年   6860篇
  2001年   6107篇
  2000年   5008篇
  1999年   3511篇
  1998年   3061篇
  1997年   3060篇
  1996年   2993篇
  1995年   2430篇
  1994年   2508篇
  1993年   2536篇
  1992年   2676篇
  1991年   2734篇
  1990年   2641篇
  1989年   2623篇
  1988年   2568篇
  1987年   2528篇
  1986年   2443篇
  1985年   3127篇
  1984年   3303篇
  1983年   2656篇
  1982年   2919篇
  1981年   2801篇
  1980年   2592篇
  1979年   2835篇
  1978年   2955篇
  1977年   2895篇
  1976年   2900篇
  1975年   2743篇
  1974年   2716篇
  1973年   2900篇
  1972年   1912篇
  1967年   1868篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
41.
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity....  相似文献   
42.
43.
Applied Magnetic Resonance - The suggested approach allowed us to derive analytical expressions for modeling the shape of solid-echo signal and its time evolution for a system of three-spin groups...  相似文献   
44.
45.
Physics of Atomic Nuclei - We have studied the mechanisms influencing production of cumulative pions and protons in the fragmentation of the incident deuterons into cumulative pions and protons...  相似文献   
46.
47.
48.
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters.  相似文献   
49.
Erosion and sediments transport processes have a great impact on industrial structures and on water quality. Despite its limitations, the Saint‐Venant‐Exner system is still (and for sure for some years) widely used in industrial codes to model the bedload sediment transport. In practice, its numerical resolution is mostly handled by a splitting technique that allows a weak coupling between hydraulic and morphodynamic distinct softwares but may suffer from important stability issues. In recent works, many authors proposed alternative methods based on a strong coupling that cure this problem but are not so trivial to implement in an industrial context. In this work, we then pursue 2 objectives. First, we propose a very simple scheme based on an approximate Riemann solver, respecting the strong coupling framework, and we demonstrate its stability and accuracy through a number of numerical test cases. However, second, we reinterpret our scheme as a splitting technique and we extend the purpose to propose what should be the minimal coupling that ensures the stability of the global numerical process in industrial codes, at least, when dealing with collocated finite volume method. The resulting splitting method is, up to our knowledge, the only one for which stability properties are fully demonstrated.  相似文献   
50.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号